Wastewater flow and E.coli transport from at-grade line sources to shallow groundwater

Amanuel Oqbit Weldeyohannes^1*, R.G. Kachanoski² and M. Dyck¹

¹Dept. Renewable Resources, 751 GSB, University of Alberta, Edmonton, AB, T6G 2H1

²Office of the President, Memorial University of Newfoundland, St. John's, NL A1C 5S7

*Presenter e-mail: aweldeyo@ualberta.ca 

A better understanding of pathogen transport under variably saturated and unsaturated conditions typical of on-site wastewater treatment systems (OWTS) is required to assess the environmental risks associated with these systems. The main objective of this research is to better understand the fate and transport of E.coli in the vadose zone and shallow saturated zone under boundary conditions characteristic of OWTS. In-situ spatial and temporal transport of E.coli and Br^- from at-grade line sources to shallow groundwater were investigated at Wetaskiwin Rest Stop, Alberta, Canada. The site was receiving a ultraviolet (UV) disinfected wastewater since 2007 via a pressurized at-grade line sources. Following a field characterization and wastewater plume delineation, a nest of piezometers (N=30 in 10 nests) were installed along the wastewater plume center of mass parallel to the direction of groundwater flow. The UV system breakdown was simulated for one month and a pulse of Br^- as conservative tracer was applied to track contaminant transport over time. Preliminary results and plans for future investigations will be presented. The research output will benefit future research on pathogens fate and transport and groundwater risk assessment plans.

Key words: On-site wastewater treatment/disposal system, Wastewater plume, Groundwater contamination.